Have a whine or humming sound when driving at speeds from about 35 mph to 75 or so, seems like when I back off of the accelerator the whine or hum gets softer as I increase speed the pitch gets higher until I reach about 75 mph then it almost goes away. Other that it runs fine, no vibrations, no other malfunctions, this is a 2003 GMC DENALI AWD w/ 120,000 miles on it, I've changed all fluids, inspected undercarriage found no leaks or loose items,
Last edited by innocenzio (7/19/2011 12:16 PM)
If the whine is throttle sensitive and changes with speed and sounds like it is coming from the rear than it could be the pinion bearings and or ring and pinion noise in the rear axle.
Getting the truck up on a lift and using a listening device like a mechanics stethoscope the mechanic can determine which bearing is making the noise, the bearings or the ring and pinion gears.
If the noise is coming from the front, there is a service bulletin on this noise, it is 03-04-17-005 dated March 2003. This is part of the service bulletin below.
Subject: Whine Noise from Front Axle (Diagnose and Replace Front Propeller Shaft with a Tuned Internally Dampened Front Propeller Shaft).
Some customers may comment on a slight whine noise from the front of the vehicle during light throttle conditions, typically at two vehicle speed ranges of 64-80 km/h (40-50 mph) and 112-129 km/h (70-80 mph).
Cause: Inherent" ring and pinion gear whine.
All gear driven units, such as automotive rear axles, produce some level of noise that cannot be eliminated with conventional adjustments and repairs. "Inherent" axle noise can be described as a slight noise heard only at a certain speed on most General Motors trucks. The presence of this noise is not indicative of a functional concern with the axle assembly. However, some customers may find that this "inherent" axle noise is unacceptable.
Correction: Replace the front propeller shaft with an internally tuned dampened shaft ONLY after diagnosis concludes that it is an "inherent" front axle noise and no physical damage or incorrect adjustment exists.
Diagnostic Information and Procedure for Front Axle Noise
Diagnostic Starting Point - Front Drive Axle (Refer to SI Document ID # 696970)
Symptoms - Front Drive Axle (Refer to SI Document ID # 696957).
Front Drive Axle Noises (Refer to SI Document ID # 700621).
Noisy in Drive (Refer to SI Document ID # 700622).
Noisy When Coasting (Refer to SI Document ID # 700624).
Intermittent Noise (Refer to SI Document ID # 700625).
Constant Noise (Refer to SI Document ID # 700631).
Noisy on Turns (Refer to SI Document ID # 700634).
You can go to your local dealer for more information on this service bulletin or you can get a copy of it at ALLDATAdiy.com.